The objectives of this study are to establish the qualitative and quantitative toxicities of CI-980 when administered to children with solid tumors refractory to standard therapy. The goal is also to establish a maximum-tolerated dose of CI-980 that results in tolerable toxicity, which is predictable and reversible. Lastly, the pharmacokinetics of the drug in relation to its toxicity will be studied. CI-980 is a novel non- cross resistant tubulin binder with good pre-clinical activity.